Circular Strip Research Articles

Multi-physics analysis of a novel circular pantograph catenary system for high-speed trains

PurposeIn high-speed trains, the energy is supplied from a high voltage catenary to the vehicle via a pantograph catenary system (PCS). Carbon pantograph strips must maintain continuous contact with the wire to ensure safety and reliability. The contact is often confined to a particular spot, resulting in excessive wear due to mechanical and thermal damage, exacerbated by the presence of an electric arc and associated electrochemical corrosion. The effectiveness and reliability of the PCS impacts on the performance and safety of HSTs, especially under high-speed conditions. To alleviate some of these adverse effects, this paper aims to propose a configuration where a circular PCS replaces the currently used pantograph strips.Design/methodology/approachTwo dynamic multi-physics models of a traditional PCS with a carbon strip and a novel PCS with a circular pantograph strip catenary system are established, and the electrical and mechanical characteristics of these two systems are compared. Moreover, a PCS experimental platform is designed to verify the validity and accuracy of the multi-physics model.FindingsA novel circular pantograph system is proposed in this paper to alleviate some of the shortcomings of the traditional PCS. Comparing with a traditional PCS, the circular PCS exhibits superior performance in both electromagnetic and thermal aspects.Originality/valueThe paper offers a new technical solution to the PCS and develops a dedicated multi-physics model for analysis and performance prediction with the aim to improve the performance of the PCS. The new system offers numerous benefits, such as less friction heat, better heat dispersion and improved catenary-tracking performance.

Laboratory and Numerical Investigation of Saltwater Intrusion Processes in a Circular Island Aquifer

AbstractA novel radial flow experimental system to study saltwater intrusion processes in an island aquifer is presented. The study investigated steady state and transient scenarios involving advancing and receding saltwater wedges in a circular island. The experimental results were simulated using the density‐coupled version of the MODFLOW‐USG code. The experimental data along with the model simulation results are employed to develop a new radial benchmark problem for testing density‐coupled models used for simulating saltwater intrusion processes. The experimental data for transient changes in toe position and freshwater storage level indicated an asymmetric pattern where the intrusion time scale is greater than the recession time scale. Numerical experiments were completed to further investigate this asymmetric effect and to intercompare the associated transient transport processes in circular and linear strip islands. We also analyzed the sensitivity of island geometry in controlling the freshwater storage levels under different recharge conditions. Modeling results show that for similar‐sized systems, circular islands are more efficient in storing freshwater than linear strip islands.

Design of a Miniaturized Printed Multi-Turn Loop Antenna for Shielding Effectiveness Measurement

This paper proposes a novel miniaturized loop antenna consisting of a multi-turn printed strip and a ring-shaped ferrite core. The lateral surface of the ferrite core is tightly wrapped by the circular multi-turn strip, which is printed on a thin, ring-shaped Styrofoam. To verify the feasibility, the proposed antenna is fabricated, and the antenna factor (AF) levels are measured using the three-antenna method from the VLF to HF band. The AF levels by measurement, theory, and simulation are 36.14 dB, 34.01 dB, and 33.6 dB at 30 kHz, respectively. In the VLF band, the antenna has a diameter of 114 mm, which is miniaturized to less than 60% compared to previous research. In addition, the proposed antenna is employed in the shielding effectiveness (SE) measurement of a small commercial cabinet to observe its suitability for SE measurement of small shielding enclosures. The SE values averaged over the frequency range from 10 kHz to 3 MHz are 5.19 dB and 14.14 dB in the horizontal and vertical polarizations.

Study on the Instability Mechanism and Grouting Reinforcement Repair of Large‐Scale Underground Stopes

The environmental conditions due to unreasonable mining in underground stopes, the slurry diffusion mechanism in the grouting reinforcement of a stope within its influence, the causes of large‐scale instability collapse, and the catastrophic stope process are analyzed, and limit upper line analysis theory and numerical analysis methods are comprehensively adopted, revealing the continuous catastrophic collapse mode of large‐scale underground stopes. The method of determining the stope instability collapse boundary and the slip surface within the range based on the theory of the maximum shear strain increment is proposed, and the diffusion radius and range of the grouting slurry during the reinforcement process, which considers the multifield coupling factors, are obtained. The results show that the U‐shaped hidden danger area formed after the collapse of the large‐scale underground stope. The influence range reaches six adjacent stopes, which are symmetrically distributed around the collapse; the mining instability is manifested as a catastrophic chain process of stress change, energy accumulation, state change, and instability collapse. The damage mode of instability collapse is a combination method of wedge collapse, circular arc rotation, triangular translation, and strip slip. According to the multiphysics coupling numerical calculation, the diffusion radius of the grouting slurry is 12 m, exhibiting an elliptical distribution. The research results can be used to comprehensively control the underground mining environment, thus effectively solving the safety problems faced by tunnel or roadway excavations above the goaf.

Heat Transfer and Pressure Drop Measurements in a High Aspect Ratio Channel With Circular Pins and Strip Fins

Abstract This paper focuses on the measurements of heat transfer enhancement and pressure drop of different pin or fin configurations in a high aspect ratio (AR = 9.57/1.2) channel. Two different pin-fin shapes including circular pins and strip fins were studied. Different pin-fin spacings for circular pins (S/D = 2, 4) and strip fins (S/W = 8, 16) were investigated, respectively. In addition, the thickness effect of the strip fin was included in this study. The regionally averaged heat transfer measurement method was used to acquire the heat transfer coefficients on two opposite featured surfaces within the test channel. For each configuration, the tested Reynolds number was ranging from 20,000 to 80,000. The results indicate that the channel with circular pins has better heat transfer enhancement and higher pressure loss than their strip fins counterparts. However, the strip fins are considered better designs in terms of thermal performance. For the gas turbine designers aim at developing an improved internal cooling feature, this work demonstrates the great potential of the strip fins as a novel and effective cooling design compared with the conventional circular pins.

A Theoretical Study on Circular Wire and Flat Strip Conductor Inductance for Magnetic Resonance-Shielded Phased-Array Circular Coils

Phased-array radiofrequency (RF) coils are commonly used for signal reception in magnetic resonance for their large spatial coverage, typical of volume coils, and for their high signal-to-noise ratio, usually associated with surface coils. The simplest design of phased-array coils is an array of circular loops whose conductor can be constituted by flat strip or circular wire cross-sectional geometry, often partially enclosed in an RF shield for minimizing electromagnetic interference. This paper proposes a method for the analytical calculation of the mutual inductance between two circular loops constituting a dual-element phased-array coil by taking into account the conductor’s geometry and the effect of an eventual RF shield.

Radiofrequency planar surface coil for magnetic resonance: When the use of a circular wire gives a noticeable advantage with respect to a flat strip conductor?

Depending on their cross-sectional shape, commonly used conductors for radiofrequency (RF) Magnetic Resonance (MR) coils can be categorized into circular wires and flat strips. Due to a more symmetrical current distribution inside conductor volume, coils constituted by wire conductors provide better overall performance in unloaded conditions with respect to the ones made of strip conductor, although wire conductors are difficult to handle for coil manufacturing and additional mechanical competencies are required. Nevertheless, the accomplishment of the best coil performance during imaging, i.e. in the presence of a sample, remains the main issue in MRI. It follows that the use of wire conductors instead of strip ones is worthwhile only if the correspondent increase in coil quality factor with sample is substantial: this is related to the ratio between sample and coil resistance.This paper proposes the application of a finite element method (FEM)-based numerical approach for separately estimating the conductor and radiative losses in planar surface loops characterized by different cross-sectional shapes (circular wire and flat strip) in conjunction with a vector potential calculation-based method for sample-induced resistance estimation. Simulation data were acquired from 5.7 to 128 MHz, for four different size loops (from 2 to 15 cm diameters), with the scope of evaluating the region in the frequency-loop diameter plane where the use of a circular wire conductor gives a noticeable advantage with respect to the flat strip in maximizing signal-to-noise ratio (SNR) in MR applications.

Development of a Low Radar Cross Section Antenna With Band-Notched Absorber

A low radar cross section (RCS) antenna designed with band-notched absorber is described. First, a dual-polarization absorber with relative bandwidth more than 80% is designed using loaded resistors. Pairs of circular slot resonators and metal strip array resonators are introduced in the absorber to realize a notch band with full reflectance in the vertical polarization, while a wide absorption band in the horizontal polarization is maintained. The proposed band-notched absorber is thus realized. Within the notch band, the absorber can be served as a metal ground for antenna; while a great RCS reduction is obtained out of the notch band and in the horizontal polarization band. Then, a dipole antenna rigorously designed is mounted above the band-notched absorber, whose operating frequency is exactly in accordance with that of the notch band. The proposed low RCS antenna is established based on assembling the dipole antenna and the band-notched absorber together. The measured results demonstrate that the proposed antenna has fairly good radiation patterns. Added to that, more than 10 dB RCS reduction in two polarizations is realized simultaneously compared with that one of a conventional dipole antenna.

Does ferrule thickness influence resistance to fracture of endodontically treated teeth?

Background:Teeth with severe crown destruction and endodontically treated may or may not present a circular strip of dental tissue located in the cervical region called ferrule.Aims:The aims of this study were to evaluate ferrule thickness influence on endodontically treated teeth (ETT) resistance to fracture.Materials and Methods:A total of 30 bovine incisor teeth were selected, endodontically treated and randomly distributed, according to the ferrule thickness: G1- no ferrule, G2 – 1 mm, and G3 – 2 mm. All the teeth were restored with prefabricated posts and composite resin. Resistance to fracture was established as the compression strength at 45° tilt at the lingual surface of the crown.Statistical Analysis Used:Data were analyzed using ANOVA and Tukey's test.Results:Resistance to fracture of G1 and G2 were significantly higher than that of G3 (P < 0.001). The pattern of fracture, common to all groups, occurred at the composite resin on the coronary portions.Conclusion:Ferrule thickness can influence the resistance to fracture of ETT.

Diversity and determination of wildlife ‘umbrella species’ in the Gunung Leuser National Park

The determination of ‘umbrella species’ in the wildlife conservation implementation is very important to be effective and directed. This study was aimed to obtain information wildlife diversity (primates and terrestrial mammals) and ‘umbrella species’ on various type of habitats to support conservation programs in the Gunung Leuser National Park (GLNP), of Besitang Watershed, North Sumatera. The research was carried for six months, from May to October 2015. The observation was made using combination of variable circular plot and strip transect methods. Determination of 'umbrella species' is done through valuating by referring to the Department of Forestry criterias (2008). Primate were identified about 6 species and terrestrial mammal of 16 species. Primate and mammal diversity index are with the category of low to moderate with abudance index between 5.60-15.32. Based onassessment criteria and consideration to high conflict potential show that ‘umbrella species’ are elephant (Elephas maximus sumatranus Temminck, 1847). The wildlife conservation implications are recommended, such as to the elephants around GLNP, i.e to increase research wildlife distribution and population, habitat protection and population pockets, to develop a database and monitoring with geographic information systems (GIS), the minimization a hunting and law enforcement as well as mitigation wildlife conflicts, such as elephants and orangutans.

Closed-form analytical solutions for assessing the consequences of sea-level rise on unconfined sloping island aquifers

Closed-form analytical solutions for assessing the consequences of sea-level rise on fresh groundwater oceanic island lenses are provided for the cases of both strip and circular islands. Solutions are proposed for directly calculating the change in the thickness of the lens, the changes in volume and the changes in travel time of fresh groundwater within island aquifers. The solutions apply for homogenous aquifers recharged by surface infiltration and discharged by a down-gradient, fixed-head boundary. They also take into account the inland shift of the ocean due to land surface inundation, this shift being determined by the coastal slope of inland aquifers. The solutions are given for two simple island geometries: circular islands and strip islands. Base case examples are presented to illustrate, on one hand, the amplitude of the change of the fresh groundwater lens thickness and the volume depletion of the lens in oceanic island with sea-level rise, and on the other hand, the shortening of time required for groundwater to discharge into the ocean. These consequences can now be quantified and may help decision-makers to anticipate the effects of sea-level rise on fresh groundwater availability in oceanic island aquifers.

Integral equation for a strip coil antenna located on a dielectric cylinder

The problem about the distribution of the surface current density in a narrow circular strip antenna as an infinitely thin perfectly conducting ribbon folded in a circle and positioned on the surface of a dielectric cylinder is reduced to a one-dimensional integral equation (IE). A method for solving the obtained IE is proposed. Complex distributions of the azimuthal component of the surface current density over the circular conductor are presented for different values of the dielectric permittivity of the cylinder.

Novel compact dual-band-notched ultra-wideband printed antenna with a parasitic circular ring strip

A simple and compact printed ultra-wideband antenna with dual-band-notched characteristics is presented. The proposed antenna is composed of a rectangular patch and a modified ground plane. The rectangular patch is etched onto a lossy FR4 substrate. A circular ring strip parasitizes the rectangular patch embedded by a U-shaped slot. Two inverted-L slits and a rectangular slit are embedded onto the ground plane. Some bandwidth enhancement and band-notched techniques are applied in the antenna structure for broadening the bandwidth and generating notches. The simulated and measured results show that the proposed antenna offers a very wider bandwidth ranging from 3.04 to 17.30 GHz, defined by the return loss less than −10 dB, with dual-notched bands of 3.30–4.20 and 5.10–5.85 GHz covering the 3.3/3.7 GHz WiMAX, 3.7/4.2 GHz C-band, and 5.2/5.8 GHz wireless local area network systems. Furthermore, the proposed antenna presents relatively high antenna gain and quasi-omnidirectional radiation patterns.

Traditional chinese medicine Zhiqiao–Houpu herb-pair induce bidirectional effects on gastric motility in rats

Ethnopharmacological relevanceZhiqiao–Houpu herb-pair (ZQHPHP), composed of Fructus Aurantii (Zhiqiao [ZQ] in Chinese) and Magnolia officinalis (Houpu [HP] in Chinese), is a traditional herbal formula that has been extensively used for treating gastrointestinal motor dysfunction. The aim of the study was to evaluate the effect and possible mechanism of ZQHPHP on gastric emptying (GE) and gastric antral smooth muscle contractility (GASMC). Materials and methodsThis study includes four parts: (a) study of ZQHPHP's effect on GE; (b) study of ZQHPHP's effect on gastric antral smooth muscle contractility (GASMC); (c) comparing the effects of ZQHPHP, ZQ and HP on GASMC; (d) study of antagonists or agonists on ZQHPHP-induced GASMC. A test meal of Evans blue was adopted to estimate GE in rats. A polygraph was used to measure GASMC in rats. ResultsThe in vivo experiments demonstrated that, at the doses of 10mg/kgbw and 20mg/kgbw, ZQHPHP could promote GE. While, at the higher dose of 30mg/kgbw, ZQHPHP delayed the GE. From the in vitro experiments we found that ZQHPHP (3–10μg/ml) concentration-dependently increased the mean amplitude of contractions in the antral circular strip compared to untreated controls. While, in the concentration of 30μg/ml, ZQHPHP prohibited GASMC. Besides, atropine blocked the stimulatory effect of ZQHPHP on GASMC and norepinephrine partly prohibited the stimulatory effect of ZQHPHP on GASMC, whereas isoproterenol showed no effect. From the in vitro experiment, we also found that ZQ and HP used together can synergistically increase gut motor. ConclusionsThe experiment indicated that ZQHPHP could induce bidirectional regulation on gastric motility. ZQ and HP used together can synergistically increase gut motor at a certain dosage. Lower dosage of ZQHPHP increases gastric motility, while higher dosage produces inhibition. In addition, the improvement of gastric motility by ZQHPHP is predominantly involved with muscarinic receptors and secondarily with alpha-receptors.

Alternative design of left-handed metamaterial based on circular resonator and wire strip for waveguide configurations with sensing and absorber applications

Abstract. An alternative design of left-handed (LH) metamaterial (MTM) for waveguide configurations is pre-sentedwithsensorandabsorberapplications.TheLHstructureisbasedontwoidenticalcircularringresonatorsconnected with a wire strip. Both simulation and experimental results show that the planar MTM has an LHresonance at ∼9.9 GHz. Surface current and magnetic field distributions at the resonance are also presentedto show the LH behavior of the structure in detail. In addition, a parametric study based on the gap size of thestructure is also provided in order to present the dependency of the LH resonance. Next, the sensing process ispresented with respect to the thickness, position, and dielectric constant variations of the superstrate layerlocated in front of the material surface. Finally, the absorption application of the structure in X-band isshown, and the results show that the absorber behaves as a perfect absorber with an absorption rate of99.99%. As a result, the proposed structure can be used in many MTM applications, such as sensor, absorber,and soon.

Integral equations formulation of plasmonic transmission lines.

In this paper, a comprehensive integral equation formulation of plasmonic transmission lines is presented for the first time. Such lines are made up of a number of metallic strips with arbitrary shapes and dimensions immersed within a stack of planar dielectric or metallic layers. These lines support a number of propagating modes. Each mode has its own phase constant, attenuation constant, and field distribution. The presented integral equation formulation is solved using the Method of Moments (MoM). It provides all the propagation characteristics of the modes. The new formulation is applied to a number of plasmonic transmission lines, such as: single rectangular strip, horizontally coupled strips, vertically coupled strips, triangular strip, and circular strip. The numerical study is performed in the frequency (wavelength) range of 150-450 THz (0.66-2.0 μm). The results of the proposed technique are compared with those obtained using Lumerical mode solution, and CST. Very good agreement has been observed. The main advantage of the MoM is its intrinsic speed for this type of problem compared to general purpose solvers.

Modeling of vision loss due to vitreous hemorrhage by Monte Carlo simulation.

Vitreous hemorrhage is the leaking of blood into the vitreous humor which results from different diseases. Vitreous hemorrhage leads to vision problems ranging from mild to severe cases in which blindness occurs. Since erythrocytes are the major scatterers in blood, we are modeling light propagation in vitreous humor with erythrocytes randomly distributed in it. We consider the total medium (vitreous humor plus erythrocytes) as a turbid medium and apply Monte Carlo simulation. Then, we calculate the parameters characterizing vision loss due to vitreous hemorrhage. This work shows that the increase of the volume fraction of erythrocytes results in a decrease of the total transmittance of the vitreous body and an increase in the radius of maximum transmittance, the width of the circular strip of bright area, and the radius of the shadow area.

WLAN/WiMAX 시스템에 적용 가능한 반원 스트립 구조를 갖는 원형 링 안테나의 설계

In this paper, a dual-band circular ring monopole antenna with semi-circular strip for WLAN(Wireless Local Area Networks)/WiMAX(World interoperability for Microwave Access) applications. The proposed antenna is based on a planar monopole design, and composed of half circular strip for dual-band operation which cover WLAN and WiMAX frequency bands. To obtain the optimized parameters, we used the simulator, Ansoft’s High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. And characteristics of gain and radiation patterns are obtained for WLAN/WiMAX frequency bands.

Clamping method improvement for preventing the return hose oil leakage by elastoplastic finite element analysis

The clamping of the return hose to the gearbox pipe end is important to prevent the oil leakage from the automotive hydraulic power steering system. In this context, this paper is concerned with the improvement of the current clamping method using a thin circular steel strip to resolve the oil leakage phenomenon. The clamping of gearbox pipe end and rubber hose by tightening a thin circular steel strip is replaced with the swaging of a circular metal sleeve. For the current and improved clamping methods, the distributions of effective stress, effective strain, and normal contact pressure at the interface between pipe and rubber hose are analyzed and compared by utilizing the elastoplastic finite element analysis. As well, the durability test for verifying the oil leakage-proof performance of the improved method is performed at the level of return hose assembly. It is observed from the numerical analysis and experiment that the return hose oil leakage is successfully resolved by improving the clamping method.

Indoor Localization by using Particle Filtering Approach with Wireless Sensor Nodes

Jennic type wireless sensor nodes are utilized together with a novel particle filtering technique for indoor localization. Target objects are localized with an accuracy of around 0.25 meters. The proposed technique introduces a new particle generation and distribution technique to improve current estimation of object positions. Particles are randomly distributed around the object in the sensing area within a circular strip of 2 STD of object distance measurements. Particle locations are related to object locations by using Gaussian weight distribution methods. Object distances from the transmitters are determined by using received RSSI values and ITU-R indoor propagation model. Measured object distances are used together with the particle distances from the transmitters to predict the object locations.